Facts about Dairy

Facts about dairy

Many people make statements about dairy, but what is really true? In this section we answer the most common queries which arise in everyday discussion. We address all those common held beliefs and myths about dairy products.

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What are the benefits of using dairy?

Milk is not only an enjoyable drink with a pleasant taste but it also has unique nutritional value. In addition, milk is used in countless ways in preparing other foods owing to its technical advantages.

Using dairy on a daily basis has several health benefits, such as:

maintaining strong bones and teeth

encouraging growth

promoting development of strong muscles

promoting weight loss (as part of a weight loss diet)

providing 10 essential nutrients, including calcium and high-quality protein, which are highly bio-available

a low-fat food or snack choice

How much milk should I drink?

It is recommended to consume three servings of dairy a day, with a portion calculated as containing 300 mg calcium. Ideally, 1300 mg calcium should be consumed per day, although the exact requirements may vary based on age and life stage. Thus, three portions of dairy will provide three-quarters (900 mg) of your daily calcium requirement, while the rest should be obtained from other food sources. Other foods high in calcium include dark, green vegetables like broccoli or spinach, sardines with bones, and almonds.

People from certain population groups have an enhanced sensitivity to milk sugar (lactose). Research has shown that among populations of Asian, southern European or African descent, individuals tend to produce less lactase with age. Lactase is the enzyme required to break down lactose.

Individuals who are sensitive to lactose find that soured products such as maas or yoghurt, can be consumed for their nutritional value without side-effects, even though 75% of the lactose is still present. The relatively high acidity of these products increases the rate of movement through the intestine and thus limits the absorption of lactose. Consuming dairy products in small quantities or using milk together with another food (e.g. cereal) is more tolerable.

Cheeses contain almost no lactose and are therefore suitable for all.

What does milk consist of?

Milk consists of 87.5% water and 12.5% solids. The solids are made up of:

3.7% fat

3.4% protein

4.8% lactose (milk sugar) • 0.6% vitamins and minerals

The most important vitamins and minerals in milk are as follows:

* RDA is the recommended daily (or dietary) allowance, i.e. the quantity of a particular nutrient which should be consumed daily in order to maintain good health.

What is pasteurisation?

Pasteurisation is a treatment process aimed at destroying pathogenic micro-organisms and greatly reducing the total number of harmful micro-organisms in the fresh product to ensure safe human consumption. Since its discovery by Louis Pasteur in 1872, the original heatbased process has been refined so as to remove most of the harmful micro-organisms from the product without causing degeneration of the sensory or nutritional characteristics.

Ultra-pasteurisation is a relatively new process that involves treating milk at a higher temperature than used for traditional pasteurisation (72 °C) but for a much shorter time. The advantage of ultra-pasteurisation is that it affords a much longer shelf life to milk kept in the cold chain compared to conventionally pasteurised milk. With modern processes, even UHT treatment causes very little damage to the nutritional value of milk, although the process may lead to a slight change in flavour.

Although heat treatment is still the most commonly used preservation treatment, other processes (e.g. irradiation) are also used to a limited extent.

How long can milk be kept?

Raw milk contains a range of micro-organisms, including those that produce lactic acid. If not kept cold, these acid-forming micro-organisms can cause raw milk to go sour within 8–24 hours, depending on the temperature. Temperatures between 20 °C and 30 °C create ideal conditions for acid-forming organisms. Although some bacteria that can make milk go bad are also supported, enough acid-forming micro-organisms are usually present under these temperature conditions to kill those that may make milk go bad. In warm conditions raw milk will therefore go sour rather than spoil.

When kept at a temperature between 4 °C and 5 °C, raw milk should safely last about four days providing good hygienic practises are adhered to. At this temperature raw milk will spoil without going sour if kept too long, because the cold-resistant micro-organisms present in milk can continue their activity without any significant restriction being imposed by lactic acid producers.

Pasteurised milk should last 6–10 days in the fridge (4–5 °C), provided it was not contaminated during processing or packaging. Ultra-pasteurised milk may last up to 21 days under the same conditions.

UHT-treated, sterilised and other long-life milk products need not be cooled. Unopened they may last for 6 months and some even as long as 18 months, without any disadvantage. Once opened UHT should be treated as fresh milk.

Why does milk spoil or go sour?

Milk contains an array of valuable nutrients, for both humans and animals. However, these nutrients are also suitable for micro-organisms, which flourish on the rich cocktail of sugar, protein, fat, vitamins and minerals contained in a moist environment.

Milk sugar (lactose) is a selective ingredient, which favours activity of acid-forming organisms that can use lactose. At ideal temperatures, souring organisms will grow fastest in raw milk. Souring agents have to be added deliberately to pasteurise (heat-treated) milk to induce souring, for example to make maas, and prevent spoilage.

Souring is a natural self-preserving mechanism of milk. Soured milk still offers a nutritious (and even refreshing) drink since none of the nutrients are lost during the souring process. However, spoilt (rotten) milk is totally unacceptable: it tastes and looks bad and may even contain toxins released during the decomposition process.

Unopened long-life milk (either UHT-treated or sterilised) does not normally go sour, except if contaminated with a large number of souring micro-organisms. It can, however, spoil as contamination from the packaging environment tends to favour the rotting organisms, which, in the absence of sufficient souring organisms, will have no competition.

How do the various milk products available on the market differ?

Low-fat milk contains 0.5–2.5% milk fat, which means that both 1% and 2% milk are classified as low fat according to legal guidelines. However, since the packaging clearly states a certain percentage of fat, the composition of the milk product must adhere to the specific claims within a certain margin of error. Pasteurised, commercially available fullcream milk contains 3.43% milk fat, while raw full-cream milk (this is milk directly from a cow without going through any process) often contains more.

This table gives the typical composition of milk.

Is milk safe?

YES milk bought in the supermarket is safe. Treating milk with an accepted process (usually heat-based) is aimed at making it safe. It does not render milk poisonous or unfit for human consumption and none of the accepted treatments (e.g. pasteurisation) has a negative effect on the physical, chemical or nutrient composition of the milk.

When will a product be considered a dairy product?

A product can be defined as dairy when it contains more than 50% milk solids. Dairy products do not include milk “blends” or artificial milk products.

According to this definition of milk, flavoured milk drinks, commercial milkshakes, cottage cheese, buttermilk, yoghurt, frozen yoghurts, full-cream ice cream, cheese and processed cheese are all regarded as milk products. However, chocolate is not considered a dairy product since the percentage of milk in chocolate is too low to have any beneficial nutritional value.

Products with a long shelf life, such as long-life and sterilised milk (coloured and flavoured) and milk powder

Products with a long shelf life which should be refrigerated mature cheese and processed cheese

Why is cow’s milk suitable for human consumption?

Worldwide, humans use milk from cows, goats, sheep, buffalo and camel to provide a valuable contribution to their nutritional needs.

You may have heard people say that cow’s milk is for calves, not humans. They believe that we should be able to obtain enough calcium from other food sources and that dairy should therefore not be consumed by humans, often advising that the entire dairy food group be excluded from the diet. However, excluding a food group completely leaves one at risk of nutritional deficiency and is therefore not recommended.

Excluding milk should be avoided. Milk provides a nutrient-rich food source and can add substantial nutritional value to your diet and contribute to the recommended daily allowance in a balanced diet. Mother’s milk is certainly not available in quantities for consumption on any other level than for infants!

How do I recognise milk allergy?

Dairy allergies more commonly known as Cow’s milk allergy (CMA), is a complex and often misunderstood disorder. A frequent misconception among the general public is the confusion between CMA and lactose intolerance. A true food allergy occurs when there is an abnormal reaction by the immune system to one or more food protein.

Being uninformed often causes people to self-diagnose milk allergy. In reality, research has shown that cow’s milk allergy affects only 2–6% of infants and 0.1–0.5% of adults worldwide.

An allergy is an abnormal immune response to one or more proteins brought on by an enhanced count of the IgE-type antibody. This reaction leads to undesirable or even dangerous symptoms. Symptoms for cow’s milk allergy may include hives (urticaria), vomiting, diarrhoea, colic, rhinitis and gastroenteritis.

A qualified health practitioner, either a medical doctor or a dietitian, can diagnose an allergy through an elimination process. Possible food sources that may cause the allergy are removed from the diet one at a time until the culprit is identified. If the patient is allergic to cow’s milk, all forms of dairy products must be avoided, including milk and flavoured milk, cheese, yoghurt, butter, ghee, ice cream, soured milk products, milk powder, etc. Food labels have to be studied carefully to determine whether a product contains milk powder, milk solids, casein or whey, since these can all lead to an allergic reaction.

Unnecessary exclusion of milk and dairy products should be avoided as far as possible. Ask your doctor, dietitian or a qualified medical practitioner for advice to treat and support your allergy so that you can avoid nutrient deficiency and harm to your body.

What is lactose intolerance?

Intolerance to a food should be distinguished from an allergy since intolerance is not a response of the body’s immune system. The intolerance is more likely caused by a shortage of an appropriate enzyme or a reaction to certain ingredients that occur in the food, whether natural or artificial.

Lactose is the natural sugar in milk of mammalian origin (including breast milk). The enzyme lactase aids in the digestion of lactose by breaking it down into two simple sugars, glucose and galactose. Lactose intolerance, therefore, is the condition where a person does not have sufficient levels of lactase to digest lactose. Bacteria that occur naturally in the colon ferment undigested lactose received from the small intestine. This fermentation process may lead to the formation of acid and gas, while the body may simultaneously attempt to dilute the concentration of the lactose by re-absorbing water from the blood. This can cause vomiting and diarrhoea. Intakes of more than 12 g lactose (typically one glass of milk) may lead to symptoms such as abdominal pain, discomfort, bloatedness, wind, cramping and diarrhoea.

Consuming small quantities of milk together with other foods and naturally fermented dairy products, such as yoghurt or maas, is recommended. Cheese contains virtually no lactose and should not have any adverse effect.

What is lactose-free milk?

Lactose-free milk contains no milk sugar. There are products in the market which are readily available at supermarkets. Lactose-free milk is normal milk processed through an UHT process and then the enzyme lactase is added. The enzyme rapidly breaks down the lactose into its component sugars glucose and galactose. Since the product does not need refrigeration, the enzymes remain active because the ambient temperature creates a favourable condition for sustained activity.

Can milk prevent osteoporosis?

Because milk is an excellent source of highly absorbable calcium, it plays an important role in maintaining bone strength. Therefore, although milk cannot prevent osteoporosis as such, it can reduce your risk of developing the condition or delay its onset.

Bone undergoes continuous remodelling, during which calcium is deposited into new bone, a process called re-sorption. The balance between bone re-sorption and deposition changes with age. During periods of growth in childhood and adolescence bone formation exceeds resorption, whereas in early and middle adulthood the two processes are relatively equal. In ageing adults, particularly among postmenopausal women, bone breakdown exceeds formation, resulting in bone loss that increases the risk of osteoporosis over time.

Calcium depletion, where more calcium is extracted from the skeleton than deposited, leads to osteoporosis. Sufficient intake of calcium during the peak growth years (ages 10–19) may prevent the onset of osteoporosis in later life or reduce the risk of developing the condition. However, to maintain bone strength, it is also important to keep up a sufficient level of dairy intake, lead an active lifestyle with enough exercise and ensure sufficient exposure to sunlight throughout life.

Can milk consumption increase my cholesterol level?

Milk fat is but one of the fats, albeit a complex fat, that forms part of a typical diet. The composition of milk fat may vary slightly, depending on factors such as the race of the animal, the production season, the geographical area in which the animal is kept, the lactation cycle of the cow and the composition of the cow’s diet.

Almost two-thirds (65%) of the fat in full-cream milk is saturated, a quarter (25%) is monounsaturated and 3% constitutes poly-unsaturated fatty acids. Saturated fat generally contributes to higher cholesterol levels, yet each saturated fat is different and varies in its ability to increase blood cholesterol.

Research has shown that certain saturated fats have a neutral, and in some cases even a lowering, effect on cholesterol levels. The saturated fatty acid in milk, oleic acid, is known to have a lowering effect on blood cholesterol levels.

Can I become overweight from using milk?

The myth that milk is fattening and leads to weight gain often makes it one of the first foods to be cut from the diet in a weight loss programme. However, the opposite is true: a diet rich in dairy, which provides sufficient calcium, allows the reduction in body fat and promotes weight loss. The weight loss potential of milk is tied to the enhanced nutritional quality offered by a dairy-rich diet. Low-fat and fat-free dairy products, e.g. milk or yoghurt, deliver positive results in a controlled-energy diet. Read more in this section about dairy and weightloss.

Weight loss is a function of your body’s energy balance: to lose weight, your body must use more energy than it takes in. A negative balance can be achieved by increasing physical activity through exercise, so that energy use exceeds intake. It is therefore important to include nutrient-rich foods in the diet without increasing the total energy intake. The kilojoule (kJ) value of a food is merely an indication of the energy content.

The secret of dairy’s contribution to weight loss is its naturally high calcium and protein content. Research has shown that the combination of nutrients in dairy, especially calcium and protein, promotes weight loss and maintenance owing to the impact on the energy metabolism. A diet rich in calcium suppresses the influx of calcium into fat cells, which, in turn, stimulates the breakdown of fat and inhibits fat storage.

Including low-fat and fat-free dairy products as part of a kilojoule restricted diet can give positive results in weight management. In addition, dairy provides a valuable source of nutrients important for healthy blood and nervous systems, sight, muscle function, a healthy skin, controlled energy levels and even the growth and maintenance of the body as a whole. Reduction or exclusion of dairy products may lead to a nutrient deficiency that could hinder optimal health.